There are many occasions where it is desirable to transfer images produced by electrostatic means to another surface.
One such requirement is that where an image is produced on a sheet or membrane containing a photoconductor and it is to be transferred to a sheet of paper or the like so that the sheet containing the photoconductor can be reused after cleaning or for the purpose of ensuring that the final copy is on plain paper and does not contain a photoconductive layer.
It will be known that there are many applications where the final image produced, for instance, by wet xerographic development methods shall be on a plain surface without any photoconductor and many ways of transferring such images have been proposed heretofore but which generally comprise bringing the photoconductive surface on which the image has been developed into contact with the receiving sheet on to which the image is to be transferred and applying pressure to cause the image to transfer.
It is also known to use a field to aid this transfer and according to such a method the two sheets may be passed between a pair of rollers which have a potential applied between them of a polarity such that the marking particles from the photoconductor sheet will be forced away from this sheet and into firm contact with the surface on which the final image is to appear and while such transfers, particularly where a biasing field is used to aid the transfer, as well as pressure, are quite satisfactory under many conditions, such methods as known heretofore generally have the disadvantage that the transfer is either only of a small proportion of the original image or the transfer can be subject to some amount of loss of definition due to the pressure applied or to the particular field used at the time and generally a really high quality transferred image may not be achieved.